Helicopter tail rotor drive system on demand speed control

ABSTRACT

Tail rotor control system is described for helicopters. A pedal position sensor operable by a pilot yields greater tail rotor RPM relative to the main rotor RPM, giving the pilot increased control over the vehicle. This proves especially useful in certain situations, such as high altitude, where increasing tail rotor speed from main rotor speed can give a pilot increased maneuverability and stability.

TECHNICAL FIELD

The present disclosure is directed to helicopter rotors and rotorcontrol systems.

BACKGROUND OF THE INVENTION

The main rotor and blades on a helicopter provide the thrust for liftoffof the vehicle. The force used to spin the main rotor and blades exertan opposite rotational force on the fuselage. Without a stabilizingforce the fuselage would spin in reaction to the main rotor and blades.The tail rotor and its blades, extending backward from the fuselage,helps to counteract the spinning force of the main rotor and blades,thereby stabilizing the fuselage.

BRIEF SUMMARY OF THE INVENTION

One embodiment under the current disclosure comprises a helicopter,comprising: a tail rotor configured to spin two or more tail rotorblades; a main rotor configured to spin two or more main rotor blades;left and right pedals configured to be manipulated by a pilot; a pedalposition sensor configured to detect a pedal position of the left andright pedals; and a controller coupled to the pedal position sensor andoperable to adjust a speed of the tail rotor, wherein if the pedalposition is greater than a first number, then the controller maintainsthe speed at a normal operating speed, and if the pedal position is lessthan the first number then the control increases the speed above thenormal operating speed until the pedal position is greater than a secondnumber.

Another possible embodiment comprises a control system for a helicopter,comprising: a pedal position sensor configured to detect a pedalposition of left and right pedals, the left and right pedals configuredto be manipulated by a pilot; and a controller coupled to the pedalposition sensor and operable to adjust a speed of a tail rotor, thecontroller operable to maintain the tail rotor at a normal operatingspeed, wherein if the pedal position crosses a first threshold number,then the controller increases the speed above the normal operating speeduntil the pedal position crosses a second threshold number.

Another possible embodiment is a method of adjusting a tail rotor on ahelicopter, comprising: detecting a pedal position by a pedal positionsensor, wherein the pedal is configured to be manipulated by a pilot andpedal position is given a number from 0 to 100; if the pedal position isgreater than a first number then applying first speed to the tail rotorby a tail rotor driveshaft gearbox; and if the pedal position is lessthan or equal to the first number, then applying, by the tail rotordriveshaft gearbox, a second speed to the tail rotor until the pedalposition is greater than or equal to a second number.

The foregoing has outlined rather broadly the features and technicaladvantages of the present invention in order that the detaileddescription of the invention that follows may be better understood.Additional features and advantages of the invention will be describedhereinafter which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiment disclosed may be readily utilized as a basis formodifying or designing other structures for carrying out the samepurposes of the present invention. It should also be realized by thoseskilled in the art that such equivalent constructions do not depart fromthe spirit and scope of the invention as set forth in the appendedclaims. The novel features which are believed to be characteristic ofthe invention, both as to its organization and method of operation,together with further objects and advantages will be better understoodfrom the following description when considered in connection with theaccompanying figures. It is to be expressly understood, however, thateach of the figures is provided for the purpose of illustration anddescription only and is not intended as a definition of the limits ofthe present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference isnow made to the following descriptions taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram of a prior art embodiment.

FIG. 2 is a diagram of a helicopter embodiment under the presentdisclosure.

FIG. 3 is a diagram of a pedal and rotor control system embodiment underthe present disclosure.

FIGS. 4A-4B are diagrams of a tail rotor drive system embodiment underthe present disclosure.

FIG. 5 is a diagram of a method embodiment under the present disclosure.

FIG. 6 is a diagram of a method embodiment under the present disclosure.

FIG. 7 is a diagram of a method embodiment under the present disclosure.

FIG. 8 is a diagram of a method embodiment under the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Prior art helicopters have a main rotor and blades, as well as a tailrotor and tail rotor blades. The tail rotor apparatus helps to providestabilizing force, otherwise the fuselage of the aircraft would spin inreaction to the spinning of the main rotor apparatus. The force appliedto the tail rotor has previously been based on the power applied to themain rotor. A mechanical interconnection runs from the main rotor to thetail rotor, and as the main rotor speed is increased or slowed, the tailrotor speed is increased or slowed as well. Applicant has found that insome situations, such as high-altitude missions, increasing the tailrotor speed relative to the main rotor can have benefits for themaneuverability and stability of the helicopter. For example, thethinner air at high altitudes means that the tail rotor speed shouldsometimes be increased greater than the standard solution allows (i.e.,setting tail rotor speed as a function of main rotor speed). Besideshigh altitude, there are situations where a helicopter would benefitfrom high power/slow flight speed conditions.

Referring now to FIG. 1 , a prior art helicopter 100 can be seen. Theterm “rotor apparatus” will be used to generally refer to a rotor, itsrespective blades, and respective components that assist in spinningthat rotor. Helicopter 100 comprises a fuselage 110, with a main rotorapparatus 120 and a tail rotor apparatus 140. Main rotor apparatuscomprises main rotor 115 and main blades 130. Tail rotor apparatuscomprises tail rotor 150 and tail rotor blades 160. Tail rotordriveshaft 135 provides a connection from the main rotor apparatus 120to tail rotor apparatus 140. As a pilot increases or decreases the speedof the main rotor 115, the speed of tail rotor 150 (including a tailrotor gearbox 170) is automatically adjusted as a constant function ofmain rotor speed.

FIG. 2 shows an embodiment under the present disclosure. Helicopter 200comprises a fuselage 210, a main rotor apparatus 220, and a tail rotorapparatus 240. Main rotor apparatus 220 comprises main blades 230 andmain rotor 215. Tail rotor apparatus 240 comprises tail rotor 250 andtail rotor blades 260. Helicopter 200 further comprises a pedal positionsensor 270 and signal conditioner 290. Pedal position sensor 270 cancomprise part of, or be coupled to flight control system or controller275. Signal conditioner 290 couples the pedal position sensor 270 to thetail rotor driveshaft gearbox 280 which drives tail rotor 250 viadriveshaft 295 and tail rotor gearbox 285. As the pedal (not shown) ispushed toward their travel extremities by the pilot, the pedal positionsensor 270 sends a signal to the tail rotor driveshaft gearbox 280 toincrease the speed of the tail rotor 250. This allows to increase thetail rotor RPM relative to the main rotor RPM. Increasing the tail rotorRPM can comprise increasing the RPM and then modulating, as furtherdescribed herein. A controller 275 can be used in lieu of the pedalposition sensor to allow the pilot to manually adjust the tail rotorspeed as desired. In some embodiments, several components, like the tailrotor driveshaft gearbox 280 and the tail rotor gearbox 170 can becombined into one component with multiple functionalities.

Helicopter typically have two pedals (for each pilot, sometimes thereare two pilots). Typically, the pilot can press the right pedal to yawright, and the left pedal to yaw left. Commonly, for helicopters made ordesigned in the United States, pushing the left pedal is required whenflight condition requires more power from the engine to maintain mainrotor RPM. For such helicopters, a preferred embodiment incorporates apedal position sensor 270 that will sense the remaining margin of theleft pedal. Other embodiments are possible.

FIG. 3 shows one embodiment of a pedal position sensor 305, tail rotorblade angle control apparatus 360, and the intervening componentsallowing for adjustment of the tail rotor blade pitch with pedals 310.As shown, pedals 310 comprise a dual control kit allowing for twopilots.

Jackshafts interconnect the right pedals together and left pedalstogether 310. Pedal position sensor 305 can comprise a portion of apedal 310 or otherwise be functional to measure the pedal position. Link325 connects to quadrant 320 which connects to cables 330. Cables 330can pass through a plurality of pulleys 345 before reaching pitch changemechanism 350 within tail rotor apparatus 360. Pitch change mechanism350 can comprise means for adjusting the pitch of the tail or blades.FIG. 3 shows an embodiment with cables 330. However, other embodimentscan utilize push pull rods or push pull cables as a means of adjustingpitch change mechanism 350 and/or tail rotor apparatus 360.

FIGS. 4A and 4B shows an embodiment of a tail rotor driveshaft gearbox480 and associated components for providing power to a tail rotor. FIG.4A shows helicopter 400 with main rotor 415, main blades 430, tail rotorapparatus 420, tail rotor 425, and tail rotor blades 428. In FIG. 4B,within the main rotor apparatus 435, mast assembly 440, rotor brake disc450, freewheel assembly 460 and driveshaft 470 can be seen. Otherembodiments are possible. For example, the rotor brake disc 450 could beinstalled adjacent to the main rotor apparatus 435 or anywhere on thetail rotor drive system 455. These components couple to what isgenerally referred to as the tail rotor drive system 455. Tail rotordriveshaft gearbox 480 can comprise a portion of the tail rotor drivesystem 455. The tail rotor driveshaft gearbox 480 can be installed atthe root of the tail rotor drive system 455 to reduce the longitudinalmoment on the center of gravity and to lower drive shaft RPM(revolutions per minute) and wear, thus increase maintenance intervaland reducing the cost per hour of operation. During normal operation thepower applied to the main rotor 415 can dictate the power applied to thetail rotor 425 via tail rotor drive system 455. However, circumstancesmay arise where the pilot desires to apply a different or greater powerto the tail rotor 425. In these cases, the pilot can increase andmodulate the output of the tail rotor driveshaft gearbox 480, such as bypedals 310 of FIG. 3 , and pedal position sensor 305 of FIG. 3 (or 270of FIG. 2 ) via signal conditioner 290 of FIG. 2 that can be coupled tothe tail rotor driveshaft gearbox 480 (analogous to tail rotor gearbox280 of FIG. 2 ). Tail rotor driveshaft gearbox 480 can apply a differentgear to power the tail rotor drive system 455, thereby adjusting thespeed of tail rotor 420.

The embodiment of FIG. 2 comprises a pedal and pedal position sensor270. However, other embodiments may incorporate a tail rotor driveshaftgearbox control system in a lever, a button, or other handle ormodulator that is operable by a pilot. For example, a dashboard in ahelicopter could comprise a lever that allows the pilot to increase andmodulate the output of the tail rotor driveshaft gearbox. In suchembodiments there would be a level position sensor that can be coupledto the tail rotor driveshaft gearbox 280 via signal conditioner 290, andso forth. A button, rotatable dial, or series of buttons could be usedas well. Some embodiments, such as a rotatable dial that allows a pilotto choose amongst a plurality of speeds for the tail rotor, may not needa position sensor. Any embodiment that allows a pilot to adjust tailrotor speed to a plurality of levels could be used.

Some helicopters have duplicate controls for a co-pilot. In suchembodiments, it may be desirable to give the co-pilot a control for thetail rotor speed as well. For example, both pilots could be given adial-based control. It is understood that pilot and copilot pedal systemare linked and work in unison therefore the previously disclosed pedalposition sensor would pedal position sensing for both the pilot andco-pilot.

Typically, helicopters have a left and right pedal for a pilot to use.The pedals are connected in that as one is pressed forward, the otherpedal must move backward. The position where the left pedal is pressedforward/down completely is called the 0 position. At 0 the right pedalwill be completely back/aft. The 50 position is where both pedals areequivalent. The 100 position is where the right pedal is pressedforward/down completely, and the left pedal is back or aft completely. Apedal position of 15 is when the left pedal is 15% from being completelypressed down, and the right pedal is 85% away from being pressed down,etc. Embodiments under the present disclosure can include a pedalposition sensor that constantly measures or detects the position of theleft pedal (or both pedals, or either pedal). Other means of measuringpedal position could also be used, like an electrical voltage value, orother means.

Once a helicopter has been turned on and after a warmup period, mainrotors and tail rotors tend to rotate at a constant RPM throughout aflight. Commonly for helicopters, main rotors tend to rotate at 300-400RPM, and tail rotors tend to rotate at 2000-2500 RPM. Other embodimentsare possible. In many helicopters, how much thrust is created by eachrotor is controlled by adjusting the pitch of the blades, not byincreasing RPM. More power is needed to maintain a constant RPM as pitchis increased because more air is being displaced. Less power is neededas pitch is decreased because less air is being displaced.

During flight, the pilot can press the left pedal to yaw left. And thepilot can press the right pedal to yaw right. Pressing the pedalsadjusts the pitch of the rotor blades, but the RPM of the tail rotorstays constant. The constant RPM is the standard operating RPM of thegiven helicopter. It has been found that in some situations, such as thehigh-altitude situations described above, it can be useful for the tailrotor RPM to be increased to above the standard operation RPM. Forexample, the standard operating RPM can be considered to be 100% power.An increased RPM can be at 104% of the standard operating RPM. Forexample, in some high-altitude maneuvers, as a pilot completely pressesforward the left pedal the pitch of the tail rotor blades will beadjusted while RPMs are at 100%. The helicopter may not yaw left as itshould due to the low air density, so greater power to the tail rotor isneeded. But in a typical helicopter, RPM is already at 100% and can't beincreased. But the standard adjustments to the pitch angle do not yieldthe desired leftward yaw desired by the pilot. The present disclosureallows the rotor power to be increased above the nominal RPM relative tothe main rotor 100%.

In a preferred embodiment, when the left pedal is manipulated toanywhere from 0 to 10, then the power or RPMs applied to the tail rotorcan be stepped up above 100% (the standard operating RPM). In apreferred embodiment, once the pedal position is moved to any position0-10, then the tail rotor RPMs are increased to 105%. The tail rotorRPMs are preferably maintained at 105% until the pedal is moved to aposition of 20 or larger. Due to hysteresis, and stability needs of theaircraft, it is preferred that the RPMs be held at 105% until high tailrotor power is no longer needed. Moving rapidly between standardoperating RPM and 105% should be avoided. For this reason, 105% RPMsshould be maintained until pedal position is 20 or greater. The pedalposition detailed above are approximate and are subject to adjustmentsdue to tail rotor profiles and helicopter models.

The chosen levels for applying greater RPMs can vary. For example, insome embodiments it could be chosen to have an increased RPM level of104%, that is applied at pedal positions of 0 to 12, and that 104% RPMis held until pedal position is 22 or greater.

Embodiments under the present disclosure can also include a failsafe.The failsafe can comprise electronics to measure the electrical signalfrom the pedal position sensor, or gearing on the tail rotor gearbox,that would prevent the tail rotor speed, or the power applied to it,from dropping large amounts. A fault in the pedal, pedal position sensorcould drop the electrical signal to zero, implying the tail rotordriveshaft gearbox should default to the increased RPM. Electronics canbe programmed to detect such sudden drops and to maintain a sufficienttail rotor power or speed. Or gearing in the gearbox can be setup toprovide similar functionality, such that sudden drops in power areprevented. Monitoring of the system can be continuous by checkingcircuitry and or momentary by actuation of the system by the pilot toconfirm availability prior to landing. For example, pressing a testbutton could momentarily increase the tail rotor RPM during flight.

FIG. 5 shows one method embodiment 500 under the present disclosure foradjusting a tail rotor. Step 510 is detecting a distance of displacementof a pedal by a pedal position sensor, wherein the pedal is configuredto be manipulated by a pilot. Step 520 is transmitting, by the pedalposition sensor, an electrical signal indicative of the position. Step530 is receiving, at a tail rotor driveshaft gearbox, the electricalsignal. Step 540 is increasing and modulating, by the tail rotordriveshaft gearbox, the speed of the tail rotor based on the electricalsignal. FIG. 6 shows a possible method embodiment 600 of building ahelicopter under the present disclosure. Step 610 is providing afuselage. Step 620 is providing a main rotor and a tail rotor. Step 630is providing a pedal position sensor configured to detect a pedalposition of left and right pedals, the left and right pedals configuredto be manipulated by a pilot, and wherein the pedal position is given bya number between 0 and 100, or a corresponding electrical signal. Step640 is providing a controller coupled to the pedal position sensor andoperable to adjust a speed of a tail rotor, wherein if the pedalposition is greater than a first number, then the controller maintainsthe speed at a normal operating speed, and if the pedal position is lessthan the first number then the control increases the speed above thenormal operating speed until the pedal position is greater than a secondnumber.

FIG. 7 shows a further method embodiment 700 under the presentdisclosure. Step 710 is detecting a pedal position by a pedal positionsensor, wherein the pedal is configured to be manipulated by a pilot andpedal position is given a number from 0 to 100. At step 720, if thepedal position is greater than a first number then applying first speedto the tail rotor by a tail rotor driveshaft gearbox. At step 730 if thepedal position is less than or equal to the first number, then applying,by the tail rotor driveshaft gearbox, a second speed to the tail rotoruntil the pedal position is greater than or equal to a second number.

It is to be understood that the description above has focused on use ofa left pedal to increase tail rotor speed, and that pedal position hasbeen described as 0 to 100 based on the left pedal. However, theteachings described herein can be implemented in position measurementsystems that use different measurement systems. For instance, 0 to 100could be based on the right pedal, or a different number system could beused. In addition, some helicopters embodiments under the presentdisclosure can use the right pedal to affect tail rotor speed. Forexample, with reference to FIG. 7 , for a helicopter with a leftpedal-based position sensor and left pedal use for increasing tail rotorspeed, the first number could be 12 and the second number could be 18for helicopters with main rotor turning counterclockwise. But for ahelicopter with main rotor turning clockwise and right pedal use fortail rotor speed, the same functionality can be achieved with a firstnumber of 88 and second number of 82. The number previously mentionedare configurable to allow applicability to different helicopter modelsand tail rotor designs. For clockwise main rotor aircraft, the method ofFIG. 7 would be adjusted to reflect that the standard RPM should bemaintained up until, for example, position 88. Then the increased RPMwould be applied until pedal position was, for example, 82 or less.

For example, a controller for a clockwise main rotor aircraft could bedescribed as: operable to adjust a speed of a tail rotor, wherein if thepedal position is less than a first number, then the controllermaintains the speed at a normal operating speed, and if the pedalposition is greater than the first number then the control increases thespeed above the normal operating speed until the pedal position is lessthan a second number.

A method embodiment 800 of controlling a helicopter tail rotor, coveringboth clockwise and counterclockwise turning main rotors can be seen inFIG. 8 . Step 810 is maintaining the tail rotor at a standard operatingRPM. Step 820 is detecting pedal position with a pedal position sensor.At step 830, if the pedal position crosses a first threshold number,then increase the speed above the normal operating speed until the pedalposition crosses a second threshold number. The method can then returnto 810.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A helicopter, comprising: a tail rotor configuredto spin two or more tail rotor blades; a main rotor configured to spintwo or more main rotor blades; left and right pedals configured to bemanipulated by a pilot; a pedal position sensor configured to detect apedal position of the left and right pedals; and a controller coupled tothe pedal position sensor and operable to adjust a speed of the tailrotor, wherein if the pedal position is greater than a first number,then the controller maintains the speed at a normal operating speed, andif the pedal position is less than the first number then the controlincreases the speed above the normal operating speed until the pedalposition is greater than a second number.
 2. The system of claim 1further comprising a failsafe, the failsafe configured to maintain asafe tail rotor speed if input from the pedal position sensor to thecontroller is lost.
 3. The system of claim 1 further comprising a testbutton operable to be pressed by the pilot, wherein pressing the testbutton momentarily increases the speed of the tail rotor during flight.4. The system of claim 1 wherein the first number is 12 and the secondnumber is
 18. 5. The system of claim 1 wherein when the controllerincreases the speed of the tail rotor then the speed is increased to105% of the normal operating speed.
 6. The system of claim 1 wherein thecontroller is coupled to a tail rotor driveshaft gearbox installed atthe root of a tail rotor driveshaft in order to adjust the speed of thetail rotor.
 7. The system of claim 1 wherein the first number is 10 andthe second number is
 20. 8. The system of claim 1 wherein the pedalposition is given by a number between 0 and 100, position 0 meaning theleft pedal is completely forward and the right pedal is completely aft,and position 100 meaning the left pedal is completely aft and the rightpedal is completely forward.
 9. A control system for a helicopter,comprising: a pedal position sensor configured to detect a pedalposition of left and right pedals, the left and right pedals configuredto be manipulated by a pilot; and a controller coupled to the pedalposition sensor and operable to adjust a speed of a tail rotor, thecontroller operable to maintain the tail rotor at a normal operatingspeed, wherein if the pedal position crosses a first threshold number,then the controller increases the speed above the normal operating speeduntil the pedal position crosses a second threshold number.
 10. Thecontrol system of claim 9 wherein position 0 means the left pedal iscompletely forward and the right pedal is completely aft, and position100 means the left pedal is completely aft and the right pedal iscompletely forward.
 11. The control system of claim 9 wherein the firstthreshold number is 10 and the second threshold number is
 20. 12. Thecontrol system of claim 9 wherein the controller is coupled to a tailrotor gearbox configured to adjust the speed of the tail rotor.
 13. Thecontrol system of claim 9 wherein the first threshold number is 88 andthe second threshold number is
 82. 14. The control system of claim 13wherein the helicopter comprises a main rotor that spins clockwise. 15.The control system of claim 9 wherein when the controller increases thespeed of the tail rotor then the speed is increased to at least 103% ofthe normal operating speed.
 16. The control system of claim 9 furthercomprising a failsafe configured to maintain tail rotor speed at aminimum level if the pedal position sensor is broken.
 17. A method ofadjusting a tail rotor on a helicopter, comprising: detecting a pedalposition by a pedal position sensor, wherein the pedal is configured tobe manipulated by a pilot and pedal position is given a number from 0 to100; if the pedal position is greater than a first number then applyinga first speed to the tail rotor by a tail rotor driveshaft gearbox; andif the pedal position is less than or equal to the first number, thenapplying, by the tail rotor driveshaft gearbox, a second speed to thetail rotor until the pedal position is greater than or equal to a secondnumber.
 18. The method of claim 17 wherein the first number is 10 andthe second number is
 20. 19. The method of claim 17 wherein the firstspeed is a normal operating speed and the second speed is 104% of thenormal operating speed.
 20. The method of claim 17 wherein pedalposition 0 indicates that a left pedal is completely forward and a rightpedal is completely aft, and pedal position 100 indicates that the leftpedal is completely aft and the right pedal is completely forward.